(a) Field of the Invention
The present invention relates to a method of controlling a battery charge level of a hybrid electric vehicle. More particularly, the present invention relates to such a method which can selectively restrict the battery charge level to prevent excessive increase in battery temperature.
(b) Background Art
The term “hybrid vehicle,” in its broadest sense, refers to a vehicle that utilizes at least two different kinds of power sources. Usually, the term refers to a vehicle that uses fuel and an electric motor, driven by a battery. Such a vehicle is more precisely called a hybrid electric vehicle (HEV).
The hybrid electric vehicle can take on many various structures. Most hybrid electric vehicles are either parallel type or series type.
The parallel type hybrid electric vehicle is configured such that the engine charges the battery and also directly drives the vehicle together with the electric motor. Such a parallel type hybrid electric vehicle has a shortcoming in that its structure and control logic are relatively complicated compared to the series type. Nevertheless, since this parallel type hybrid electric vehicle is efficient in that it utilizes the mechanical energy of the engine and the electric energy of the battery simultaneously, it is widely adopted in passenger cars, etc.